Hypodermic needles with syringes have been in extensive use in the medical field for injecting drugs into a patient, and inoculation against disease, for example. There is a continuing problem of injury to doctors, nurses and technicians using such hypodermic devices who become wounded by the needles when they are inadvertently dropped, or accidentally knocked from their hands on movement of the patient. In addition to physical puncture by the needle which, in itself, may be relatively minor, there is the more serious matter of infection with a disease of the patient which can be quite dangerous or even result in death. One very serious disease which can be transmitted in this manner is AIDS.
It is known to reduce needle injury exposure by placing the needles in a puncture resistant container and disposing of the container with included needle. This approach is satisfactory once the needles are in the container; however, it has been found that a substantial percentage of needle injuries result closely adjacent the time of actual use of the needle as a result of being jostled or otherwise dropping the hypodermic needle and syringe inadvertently puncturing the doctor, nurse or technician.
In the past devices have been available which required manually placing a cover over the needle at the conclusion of its use. However, these devices could not readily be operated with one hand, and, in fact, if this were tried there would be an increased possibility of injury occurring.
U.S. Pat. No. 4,850,977, BUTTON ACTIVATED AUTOMATIC NEEDLE SHEATH FOR DISPOSABLE SYRINGE, by the same inventor as the present application, discloses a sheath which can be moved into covering and uncovering relation to the needle by finger actuation of a lever arm located on the outside surface of the hypodermic syringe. Although the device can be operated with one hand alone, the hand must be shifted around a certain extent to effect actuation and the hypodermic device can be dropped at this time possibly resulting in injury.
In a further U.S. Pat. No. 4,863,434, AUTOMATIC NEEDLE SHEATH FOR DISPOSABLE SYRINGE, by this same inventor a movable protective sheath for a hypodermic syringe has a ball-like member received within an expandable undersize opening for holding the sheath in the needle-exposed relation. On pressing the plunger a slight amount farther after emptying the hypodermic barrel, the ball-like member is forced from a locking opening and a coil spring drives the sheath into needle-covering position. This device can be operated with one hand, also.